PCT patent application PCT/US16/39802 describes active matrix driven display devices that combine organic light emitting diodes (OLEDs) that emit light from a structure comprising a photonic crystal with photoluminescent overlays that are energized into light emission by absorption of light entitled by the OLEDs. Two types of devices are described. The first type combines a feedback enhanced OLED devices (FE-OLED) of the type described in U.S. Patent Application Publication Number 20040069995 with photoluminescent material overlays. The second type of device described combines band edge emission enhanced OLED devices (BE-OLEDs) of the type described in International Patent Application Number PCT/US16/38479 with photoluminescent material overlays. Light from a matrix array of the OLED devices is absorbed by a Corresponding matrix array of photoluminescent material pixels or subpixels that overlay the OLED devices and are spatially registered to them.
In both of the types of devices described above the display functions because the OLEDs produce light by stimulated emission of light within a structures comprising one or more 1-D photonic crystals and as such are vertically emitting. This vertical emission of light is well collimated and as a result there is no crosstalk such as would occur if light from one OLED in the matrix was absorbed by a subpixel of material overlaying an adjacent OLED in the matrix array. Thus, the vertical emission properties of the FE-OLEDs or BE-OLEDs make production of useful device possible. Active matrix OLED displays of this type arc advantageous in that all of the OLED devices in the matrix array can produced from the same violet or deep blue light emitting OLED materials thus considerably reducing the number of manufacturing process steps as compared to an full color, active matrix display that utilizes an array of three kinds of OLEDs that emit red, green, and blue light respectively. Furthermore, since it has been demonstrated that BE-OLEDs can produce light with high power efficiency (e.g. over 300 lumens/waft), active matrix displays of this type can be made to be much more energy efficient than conventional active matrix OLED displays.
A problem with both the FE-OLED-based and BE-OLED-based displays described in PCT/US16/39802 is that in order to build up the required photonic crystal structures many layers (around sixteen) of transparent insulating layer must be vacuum deposited. Therefore, even though the use of OLEDs emitting only one color of light reduces the number of manufacturing steps, the manufacturing process will still be costly.